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IX/20 The Fourth BATSE Burst Catalog (Paciesas+ 1998)
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The Fourth BATSE Burst Catalog
Paciesas W.S., Meegan C.A., Pendleton G.N., Briggs M.S.,
Kouveliotou C., Koshut T.M., Lestrade J.P., McCollough M.,
Brainerd J.J., Hakkila J., Henze W., Preece R.D., Mallozzi R.S.,
Fishman G.J.
============================================================================
ADC_Keywords: Gamma rays
Mission_Name: CGRO
Description:
This is the fourth catalogue of the BATSE instrument on board of the
Compton Gamma-ray Observatory, launched on April 5, 1991. It contains
the locations and times for 1637 triggered gamma-ray bursts observed
from 19 April, 1991 until 29 August, 1996.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
4b.dat 88 1637 Basic 4B catalogue.
4bcom.dat 86 2344 Comments table
4bdur.dat 52 1234 Duration table
4bexp.dat 51 37 BATSE exposure table
4bflux.dat 157 1292 Flux values for BATSE triggers
4bmax.dat 46 912 Cmaxmin table
4btric.dat 51 30 Trigger criteria table
4btris.dat 41 20 Exposure vs peak flux table
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See also:
http://cossc.gsfc.nasa.gov/cossc/batse/4Bcatalog/4b_catalog.html :
4B Home page
Description of Table 4b.dat:
This file specifies the locations and times for 1637 triggered
gamma-ray bursts observed from 19 April, 1991 until 29 August, 1996.
It therefore includes the data from the 3B catalog. The only revisions
from the 3B catalog are improved locations for the triggers #741,
2311, and 3155.
Bursts since the end of the 1B catalog (March 1992) occurred when the
GRO tape recorders were experiencing numerous errors. Consequently,
there are gaps in the data of many bursts that preclude valid
measurement of peak flux, peak rate, fluence, or duration. Peak rates
on the 1 second timescale from each detector are almost always
available. These data (called MAXBC rates) can be used to determine
burst location. Previous difficulties with this data type have been
largely removed, and we now believe that the systematic errors for
MAXBC-located bursts are the same as for bursts located with other
data types. It is still true however, that the MAXBC-located bursts
usually have larger statistical errors than would be the case if
another data type were available. The comments table provides "L"
comments for MAXBC-located bursts. A number of CGRO and BATSE flight
software changes have significantly reduced the problem of data gaps
since March of 1993.
The on-board software determines when a trigger occurs. When a burst
trigger occurs, subsequent triggers are disabled for an accumulation
period, during which the BATSE burst memories accumulate data. The
accumulation period was 242 seconds until Dec 17, 1992, and from Jan
8, 1996 to Feb 25, 1997. At all other times it has been 573 seconds.
The stored burst data are then transmitted; the readout time for all
triggers was 90 minutes until Dec 17, 1992. At that date, the flight
software was revised to suspend readouts during telemetry gaps and to
truncate readouts of weak events. This resulted in a variable readout
time. During the burst data readout, the 64 ms threshold is revised to
correspond to the maximum rate attained by the current burst, and
triggering is disabled on the 256 ms and 1024 ms timescales. Bursts
intense enough to trigger over this revised 64 ms value are termed
"overwrites". They appear as triggers in this file, with the overwrite
flag is set to 'Y'.
The BATSE trigger numbers correlate all the files for this catalog.
The trigger number is a running sequence of BATSE triggers which
include cosmic bursts, solar flares and other events. The sequence
begins with trigger 105 and ends with trigger 5586.
Each burst has a unique catalog name. These BATSE catalog names later
may be incorporated into a multi-spacecraft catalog with "GB" or "GRB"
replacing this designation of "4B". The characters "4B " begin every
BATSE catalog burst name, followed by the "yymmdd" of the burst.
"yymmdd" is the two digit year, two digit month, and two digit day.
When more than one gamma-ray burst occurs on one day, those bursts
have a single letter suffix (B,C,D...), generally in order of
intensity. Example: 4B 920503B refers to the second brightest burst
that triggered BATSE May 3, 1992. The brightest burst on that day will
have no suffix.
The burst trigger time is the end of the interval (64, 256 or 1024 ms)
on which the burst triggered the detector.
The error in angular location is the radius of a circle having the
same area as the 68% confidence ellipse defined by the formal
covariance matrix from a chi^2^ fit on the assumption of normal
errors. The error is based solely on the Poisson uncertainty in the
BATSE measurement of burst flux by each Large Area Detector. There is,
in addition, an RMS systematic error of approximately 1.6 degrees.
Adding 1.6 degrees in quadrature to the error in the table yields our
estimate of the 68% confidence interval for the burst location error.
The statistical error is believed to be Gaussian. The systematic error
distribution has a more extended tail than a Gaussian.
Byte-by-byte Description of file: 4b.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- TrigNo [105/5586] The BATSE trigger number
6- 15 A10 --- 4B The BATSE Catalog burst name, from obs. date
19- 27 F9.1 d JD The Julian Date (TJD) of the trigger
29- 37 F9.3 s Time The time in decimal seconds of day (UT)
of the trigger
39- 45 F7.3 deg RAdeg Right ascension (J2000) in decimal degrees
47- 53 F7.3 deg DEdeg Declination (J2000) in decimal degrees
55- 61 F7.3 deg GLON Galactic longitude in decimal degrees
63- 69 F7.3 deg GLAT Galactic latitude in decimal degrees
71- 76 F6.3 deg PosErr Radius in decimal degrees of positional error box
78- 84 F7.3 deg Angle Angle in decimal degrees of geocenter (1)
86 A1 --- PrevFlag [YN] Overwrite flag: Y(true) if this burst
overwrote an earlier, weaker trigger.
N(false) otherwise
88 A1 --- NextFlag [YN] Overwritten flag: Y(true) if this burst was
overwritten by a later, more intense trigger.
N(false) otherwise
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Note (1): The angle between the burst and the nadir, as measured from the
satellite
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Byte-by-byte Description of file: 4bcom.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- TrigNo [105/5586] BATSE trigger number
6 A1 --- Flag [QAOLT] Comment flag (1)
8- 86 A79 --- Text Comment
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Note (1): Q : comments on data quality
A : additional observations by other instruments
O : general comments
L : comments on the gamma-ray burst coordinates
T : comments on the gamma-ray burst duration
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Description of Table 4bdur.dat:
This table contains values for T90 and T50, quantities related to
burst duration, for 1234 gamma-ray bursts that triggered the BATSE LAD
detectors between April 1991 and 29 August 1996. T90 and T50 are
calculated using data summed over the 4 LAD discriminator channels and
using data summed over only those detectors that satisfied the BATSE
trigger criteria.
Users must note that T90 and T50 are not available for those bursts
which suffer from data gaps during the event; the integration
procedure inherently fails in these cases. However, visual estimates
of the burst duration are provided in the BATSE Comments table for
those bursts with sufficient data coverage. Users may also find other
pertinent comments concerning the calculated value of T90 and T50 in
the BATSE COMMENTS table, and it is highly recommended that the
COMMENTS table be consulted before any distribution selected on T90 or
T50 is used.
The measurements for trigger 148 were recalculated after errors in the
3B values were brought to our attention by Jay Norris.
Byte-by-byte Description of file: 4bdur.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- TrigNo [105/5586] The BATSE trigger number.
6- 12 F7.3 s T50 T50, interval covering 50% of the counts (1)
14- 19 F6.3 s e_T50 Uncertainty in T50
21- 28 F8.3 s T50start The start time of the T50 interval, relative
to the trigger time in table 4b.dat (2)
30- 36 F7.3 s T90 T90, interval covering 90% of the counts (3)
38- 43 F6.3 s e_T90 Uncertainty in T90
45- 52 F8.3 s T90start The start time of the T90 interval, relative
to the trigger time in table 4b.dat (4)
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Note (1): T50 measures the duration of the time interval during which
25% to 75% of the total observed counts have been detected.
Note (2): The start of the T50 interval is defined by the time at which
25% of the total counts have been detected, and the end of the
T50 interval is defined by the time at which and 75% of the
counts have been detected.
Note (3): T90 measures the duration of the time interval during which
5% to 95% of the total observed counts have been detected.
Note (4): The start of the T90 interval is defined by the time at which
5% of the total counts have been detected, and the end of the
T90 interval is defined by the time at which 95% of the total
counts have been detected.
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Description of Table 4bexp.dat:
The exposure table specifies the fraction of the time that a burst at
a particular point on the sky is detectable by BATSE, and accounts for
earth blockage, SAA passages, times when the burst trigger is
disabled, and times when a burst readout is in progress. It is a
function of declination only. The burst is assumed bright enough to
exceed the trigger threshold. A separate efficiency correction must
also be included in analysis of burst rates as a function of peak
flux. This efficiency is provided in a separate table; work is in
progress to improve the efficiency calculation by including
atmospheric scattering and handling of telemetry gaps. Due to the
failure of the GRO tape recorders and the presence of telemetry gaps
in the post-1B data, a different algorithm was used in preparing this
table than was used for the 1B catalog. The new algorithm not only
handles telemetry gaps, but is also more accurate in computing SAA
passages. In addition, the old algorithm excluded time intervals
during which the trigger thresholds were not at their standard
settings of 5.5 sigma in each trigger timescale, while the current
algorithm does not. A separate table is provided that specifies the
history of the trigger thresholds. The recomputed 1B exposure is
higher (0.42 versus 0.38), due primarily to the inclusion of times
when thresholds were not at 5.5 sigma. The galactic dipole moment of
the sky exposure has changed by about 0.005, due primarily to the more
accurate accounting for the SAA. The change in the galactic quadrupole
moment is negligible. In the exposure table below, the declination is
given in degrees, and the exposure fraction at that declination is
given for each of the cumulative catalogs (1B through 4B), and for
each subset that was added to make the next catalog. In the previous
exposure tables, the exposure was an average over a range of
declinations of typically about 10 degrees. Here, the exposure applies
to a specific declination. Additional statistics are provided at the
end of the table. The average exposure is the average over the sky of
the declination-dependent exposure fraction. Total time is the time
between the start and the end of the catalog subset, in units of 10^6
seconds. Total exposure, the product of the previous two numbers, is
the total time, in units of 10^6 seconds and averaged over the sky,
that BATSE was sensitive was sensitive to bursts for that catalog
subset. The values of and -1/3 are the
galactic dipole and quadrupole moments of the exposure. The values of
and -1/3 are the dipole and quadrupole moments
in the equatorial coordinate system. The uncertainty in the exposure
fractions are roughly estimated at about 4%. Possible sources of
systematic error in the moments are currently under study, but are
expected to be less than 0.003 for the galactic moments.
Byte-by-byte Description of file: 4bexp.dat
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Bytes Format Units Label Explanations
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1- 3 I3 deg DEd [-90/90] Declination (1)
5- 11 F7.5 s 1B 1B exposure
13- 19 F7.5 s 2B-1B 2B-1B exposure
21- 27 F7.5 s 3B-2B 3B-2B exposure
29- 35 F7.5 s 4B-3B 4B-3B exposure
37- 43 F7.5 s 3B 3B exposure
45- 51 F7.5 s 4B 4B exposure
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Note (1): Average Exposure:
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1B 2B-1B 3B-2B 4B-3B 3B 4B
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Average Exposure
factor 0.425 0.478 0.507 0.494 0.477 0.483
Total Time (10^6s) 27.9 31.1 49.1 61.36 108.1 171.5
Total Exposure(10^6s) 12.05 14.9 24.9 30.31 51.6 81.9
No. of bursts 260 325 537 515 1122 1637
-0.008 -0.009 -0.009 -0.008 -0.009 -0.009
-1/3 -0.004 -0.004 -0.004 -0.004 -0.004 -0.004
0.017 0.018 0.019 0.017 0.018 0.018
-1/3 0.025 0.024 0.024 0.024 0.024 0.024
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Byte-by-byte Description of file: 4bflux.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- TrigNo [105/5586] BATSE trigger number
6- 15 E10.3 mW/m2 F1 Fluence for channel 1 (20-50 keV)
17- 26 E10.3 mW/m2 e_F1 Error in F1 (1)
28- 37 E10.3 mW/m2 F2 Fluence for channel 2 (50-100 keV)
39- 48 E10.3 mW/m2 e_F2 Error in F2 (1)
50- 59 E10.3 mW/m2 F3 Fluence for channel 3 (100-300 keV)
61- 70 E10.3 mW/m2 e_F3 Error in F3 (1)
72- 81 E10.3 mW/m2 F4 Fluence for channel 4 (E > 300 keV) (4)
83- 92 E10.3 mW/m2 e_F4 Error in F4 (1)
94-100 F7.3 ct/cm2/s F64ms Peak flux on the 64ms time scale (3)
102-106 F5.3 ct/cm2/s e_F64ms Error in F64ms (1)
108-114 F7.3 0.1s T64ms Time of F64ms (2)
116-122 F7.3 ct/cm2/s F256ms Peak flux on the 256ms time scale (3)
124-128 F5.3 ct/cm2/s e_F256ms Error in F256ms (1)
130-136 F7.3 0.1s T256ms Time of F256ms (2)
138-143 F6.3 ct/cm2/s F1024ms Peak flux on the 1024 time scale (3)
145-149 F5.3 ct/cm2/s e_F1024ms Error in F1024ms (1)
151-157 F7.3 0.1s T1024ms Time of F1024ms (2)
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Note (1): The errors are one sigma statistical errors.
Note (2): The peak flux times are expressed in decimal seconds relative
to the burst trigger time for the end of the interval in which
the flux was calculated.
Note (3): The peak flux energy range is 50-300 keV, coinciding with the
energy range of the nominal BATSE on-board burst trigger.
Note (4): Since channel 4 is an integral channel, fluences given for
this channel are quite sensitive to the assumed spectral form.
Spectral analyses in this energy range should be performed with
higher resolution data types. Many of the bursts between March
1992 and March 1993 have significant gaps in the data and are
not included in the table.
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Description of Table 4bmax.dat:
This table specifies the peak count rate in units of the threshold
count rate, and the threshold count rate. The table contains 912
triggered bursts observed from launch until 29 August 1996. Many
bursts are not included, particularly after March of 1992, since
insufficient data exist to determine either the peak counts or the
threshold.
The BATSE on-board software tests for bursts by comparing the count
rates on the eight large-area detectors to threshold levels for three
separate time intervals: 64 ms, 256 ms, and 1024 ms. A burst trigger
occurs if the count rate is above threshold in two or more detectors
simultaneously. The thresholds are set by command to a specified
number of standard deviations above background (nominally 5.5{sigma}).
Background rates are recomputed every 17 seconds. The thresholds
exhibit a coarse quantization that results from truncating the square
root of the 64 ms count rate. Since we require that rates be above the
thresholds of at least two detectors, the trigger threshold is
determined by the threshold of the second most brightly illuminated
detector.
When a burst trigger occurs, subsequent triggers are disabled during
the accumulation period when the BATSE burst memories accumulate data.
These data are then transmitted. During this readout period, the 64 ms
threshold is revised to correspond to the maximum rate attained by the
current burst, and triggering is disabled on the 256 ms and 1024 ms
timescales. Bursts intense enough to trigger during this readout
period are termed "overwrites". They are recognized in the table by
the value of -999 in the threshold columns for 256ms and 1024ms.
Byte-by-byte Description of file: 4bmax.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- TrigNo [105/5586] BATSE trigger number
6- 13 F8.3 s CMax64 ?=-999.000 Maximum counts in the second most
brightly illuminated detector divided by the
threshold count rate on the 64 ms timescale
15- 18 I4 --- T64 ?=-999 Trigger threshold on the 64 ms timescale.
It is the number of counts in 64 ms required
to trigger the second most brightly illuminated
detector for this particular burst (1)
20- 27 F8.3 s CMax256 ?=-999.000 Maximum counts in the second most
brightly illuminated detector divided by the
threshold count rate on the 256 ms timescale.
29- 32 I4 --- T256 ?=-999 Trigger threshold on the 256ms timescale.
It is the number of counts in 256 ms required
to trigger the second most brightly illuminated
detector for this particular burst (1)
34- 41 F8.3 s CMax1024 ?=-999.000 Maximum counts in the second most
brightly illuminated detector divided by the
threshold count rate on the 1024 ms timescale.
43- 46 I4 --- T1024 ?=-999 Trigger threshold on the 1024ms timescale.
It is the number of counts in 1024 ms required
to trigger the second most brightly illuminated
detector for this particular burst (1)
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Note (1): Since a trigger can occur on any of the three timescales, there are
often cases in which the maximum rate will be below threshold on one
or two of the timescales. The value of V/Vmax can be determined for
any burst by selecting the maximum of the three peak rates, raised to
the -3/2 power. Many bursts have unknown counts or thresholds on one
or more timescales. These are marked by a "-999" in the table.
This can happen for one of the following reasons:
1. If the trigger occurs on the 64 ms timescale during the peak 256 ms
rate, then the peak 256 ms rate is not found.
2. If the 64 ms peak rate never exceeds the 64 ms threshold, and it
occurs before the trigger time, then the peak 64 ms rate is not
found.
3. If the 256 ms peak rate never exceeds the 256 ms threshold, and it
occurs before the trigger time, then the peak 256 ms rate is not
found.
Note that items 2 and 3 do not affect V/Vmax, since these peak rates do
not exceed threshold. Item 1 can on rare occasions lead to an
overestimate of V/Vmax.
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Description of Table 4btric.dat:
The BATSE instrument can trigger on various energy ranges and photon
count rate thresholds. This provides an opportunity to selectively
monitor for transient events with characteristic spectral properties.
For instance, the instrument is most sensitive to gamma-ray bursts
when the trigger energy covers 50 keV to 300 keV, and it is most
sensitive to terrestrial gamma-ray flashes when the trigger energy is
100 keV and above. Changes in count threshold can affect the
triggering on event of a particular duration or characteristic peak
flux. For instance, a high threshold on the 1024 ms timescale and a
low threshold on the 64 ms timescale when triggering on the energy
range 20 keV to 100 keV makes the instrument more sensitive to soft
gamma-ray repeaters and less sensitive to solar flares. The table
below gives the starting date and time for each trigger criterion used
by the BATSE instrument.
This table was last updated on May 1, 1997.
Byte-by-byte Description of file: 4btric.dat
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Bytes Format Units Label Explanations
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1- 8 A8 "DD/MM/YY" Date Date on which the trigger was changed
10- 16 I7 d TJD ? Julian day
17 A1 --- --- [/] Separator
18- 22 I5 s SOD ? Time of day for the trigger change
24- 30 A7 --- Chan Channels used for triggering (1)
32- 35 F4.1 --- T64 ? Trigger threshold above the background count
rate on the 64 ms timescales (2)
37- 41 F5.2 --- T256 ? Trigger threshold above the background count
rate on the 256 ms timescales (2)
43- 46 F4.1 --- T1024 ? Trigger threshold above the background count
rate on the 1024 ms timescales (2)
48- 51 I4 --- TrigNo ? First trigger occurring
under the new criterion
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Note (1): The channel numbers correspond to the following energy bands:
channel 1 is 20 keV to 50 keV
channel 2 is 50 keV to 100 keV
channel 3 is 100 keV to 300 keV
channel 4 is 300 keV and above
Note (2): In units of standard deviation
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Description of Table 4btris.dat:
BATSE will generate a burst trigger if the count rate in two or more
detectors exceeds a threshold specified in units of standard
deviations above background (nominally 5.5). The rates are tested on
three time scales: 64 ms, 256 ms and 1024 ms. The energy range is
nominally 50 keV to 300 keV. These efficiencies apply only to the
nominal thresholds and energy range. A history of the thresholds and
energy range settings is provided in the Trigger Criteria Table. The
threshold in flux units depends on the background rate and the sky
location relative to the detector normals. The following table gives
the efficiency for generating a burst trigger as a function of peak
flux on each of the three trigger time scales. An efficiency of 100%
indicates that a burst will always generate a BATSE trigger if it is
above the horizon and burst triggering is enabled. Corrections for
earth blockage and other flux-independent effects can be made using
the sky exposure map. The effects of atmospheric scattering are not
included in this table. As a result, the efficiencies at low fluxes
are underestimated. The thresholds are sensitive to the spectral shape
of a burst. The threshold for a hard burst is lower than the threshold
for a softer burst. The table assumes a power-law spectrum with an
exponent of -1.5. For an exponent of -2.5, the lower thresholds
increase by approximately 20%.
Byte-by-byte Description of file: 4btris.dat
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Bytes Format Units Label Explanations
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1- 5 F5.3 ct/cm2/s T64 64 ms Threshold
7- 13 F7.3 % E64 64 ms Efficiency
15- 19 F5.3 ct/cm2/s T256 256 ms Threshold
21- 27 F7.3 % E256 256 ms Efficiency
29- 33 F5.3 ct/cm2/s T1024 1024 ms Threshold
35- 41 F7.3 % E1024 1024 ms Efficiency
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History: this catalog was copied from
http://cossc.gsfc.nasa.gov/cossc/batse/4Bcatalog
in February 1998.
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(End) Patricia Bauer [CDS] 20-Feb-1998